Jean-Étienne Guettard (September 22, 1715 - January 7, 1786), French naturalist and mineralogist, was born at Etampes .

In boyhood he gained a knowledge of plants from his grandfather, who was an apothecary, and later he qualified as a doctor in medicine. Pursuing the study of botany in various parts of France and other countries, he began to take notice of the relation between the distribution of plants and the soils and sub-soils. In this way his attention came to be directed to minerals and rocks.

In 1746 he communicated to the Academy of Sciences in Paris a memoir on the distribution of minerals and rocks, and this was accompanied by a map on which he had recorded his observations. He thus, as remarked by WD Conybeare, first carried into execution the idea, proposed by of his journeys he made a large collection of fossils and figured many of them, but he had no clear ideas about the sequence of strata.

He made observations also on the degradation of mountains by rain, rivers and sea; and he was the first to ascertain the existence of former volcanoes in the district of Auvergne. He died in Paris on the 7th of January 1786.

His publications include:

• Observations sur les plantes (2 vols, 1747)
• Histoire de la découverte faite en France de matières semblables à celles dont la porcelaine de la Chine est composée (1765)
• Mémoires sur différentes parties des sciences et arts (5 vols, 1768-1783)
• Mémoires sur la minéralogie du Dauphiné (2 vols, 1779).

See The Founders of Geology, by Sir A Geikie (1897).